R

Rupester

Well Known Member
Anybody have a good method for "cheating" holes to one side when enlarging? My results at same are mixed at best, given the larger bit always wants to center in the previous hole.
Why do I ask? My QB fuse has the top engine mount holes 1/8"+ wider than the engine mount ... I need to cheat to the inside 1/8"+ when enlarging the QB 1/4" holes to 3/8" for the bolts. These are holes I cannot afford to screw up.
 
Small round file. Elongate the hole in the direction of desired movement to the desired width. Then file the sides out to near the new diameter. By then the drill should center correctly.
 
Off center

Mel's method has worked for me, even just filing one axis. Also using a step drill with a side load works fine in lighter AL sheet. Good luck. Bill
 
drill jig bushings

MSC Industrial Supply is an excellent source for the hardened bushings. mscdirect.com. Ricks picture shows some shoulder bushings. By making one block with a liner these shoulder bushings of various sizes can be used in the liner. Normally a locking screw is used to hold the shoulder bushing in place. For example using three different bushings in the same liner a pilot hole, 1/64 undersize reamer drill and reamer can be used. MSC also has fractional reamers for better fit on critical bolts, example .373 reamer for AN6 bolts which usually run around .3725/.373. The MSC print catalog is 4-5 inches thick.
 
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